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<h2 style="margin:0; background:#cedff2; font-size:120%; font-weight:bold; border:1px solid #a3b0bf; text-align:left; color:#000; padding:0.2em 0.4em;">Article of the Week - [[Feather - Anatomy & Physiology|Feather]]</h2>

<h2 style="margin:0; background:#cedff2; font-size:120%; font-weight:bold; border:1px solid #a3b0bf; text-align:left; color:#000; padding:0.2em 0.4em;">Article of the Week - [[Process of Micturition - Anatomy & Physiology|Process of Micturition]]</h2>

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[[image: Parts of the Feather.jpg|thumb|250px|right|Parts of a Contour Feather:

[[image: sumlutshcemtri.jpg.|thumb|250px|right|A schematic overview of the lower urinary tract showing the nerves and muscles involved in micturition]]

<br/>1. Vane<br/>2. Rachis<br/>3. Barb<br/>4. Afterfeather<br/>5. Calamus]]

'''Micturition is the normal process of the passive storage and active voiding of urine.'''

Feathers are one of the epidermal growths that form the distinctive outer covering, or '''plumage''' of birds. They are the outstanding characteristic that distinguishes the Class '''Aves''' from all other living groups. 

==Structure & Function==

After entering the renal pelvis the modification of the urine is over in all domestic species other than the horse where mucin is added.  The urine passes along the [[Ureters - Anatomy & Physiology| ureters]] and enters the [[Urinary Bladder - Anatomy & Physiology|bladder]].  It is here that the urine is stored until it is to be voided.  Urine is not constantly excreted and it is only when there is a significant amount present in the bladder that the process of voiding occurs.  Both the [[Urinary Bladder - Anatomy & Physiology| Bladder]] and the [[Urethra - Anatomy & Physiology| Urethra]] have smooth muscle and thus receive autonomic influence with regard to their activity.  However the urethra also has an element of skeletal muscle giving the animal some degree of conscious control over the voiding of urine.

The bladder has stretch receptors (alpha receptors in the neck and trigone, and beta receptors in the body) which detect fullness of the bladder. These impulse to the pelvic nerves and so to the sacral spinal cord. The urethra has afferents detecting flow, distension and pain that go via the pudendal nerve to the sacral cord.

Cryptic colouring (camouflage)

 

[[Process of Micturition - Anatomy & Physiology|Click here to read more]]

In most birds, the body is divided into areas that contain feather ''tracts'', '''pterylae''' and areas that do not, '''apteriae'''.  The location and the number of tracts varies between species.  By originating from tracts rather than being randomly distributed, feathers can smoothly overlap and conform to the natural contours of the body.  By laying feathers over apteriae, air can be trapped beneath, providing [[Thermoregulation in Skin - Anatomy & Physiology|insulation]].

 

 

[[Feather - Anatomy & Physiology|Click here to read more]]

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